Apparatus for axial compression of windings

ABSTRACT

An apparatus for the axial compression of windings in electrical machines and power transformers, during the manufacture thereof, is provided with a plurality of mechanisms for developing a compressive force. Each mechanism includes at least one arm having a free lower end adapted to slidingly engage a surface. The arms are each inclined at an acute angle relative to the surface. The mechanisms further include a vertically extending rod for transmitting a compressed force to the winding. The rod is connected at its lower end to the upper ends of the arms such that the weight of the winding acts to decrease the acute angle of the arms with the surface whereby the rod is pulled down to produce a desired axial compressed force.

United States Patent Inventors Yakov Zinovievich Checheljuk Dnepropetrovskoe Shosse, 62; Gennady lvanovich Pshenichny, Ulitsa Kremlevskaya, 27, kv.8; lvan Pavlovich Yakimenko, Ulitsa Schastlivaya. 5, kv.l l,

Zaporozhie, U.S.S.R. Applv No. 774,015 Filed Nov. 7, 1968 Patented Jan. 26, 1971 APPARATUS FOR AXIAL COMPRESSION OF WINDINGS 71.5, 89, 92, 92.1; 72/137, 435; 242/79, 83; 100/214, 264, (inquired) [56] References Cited UNITED STATES PATENTS 3,212,429 10/1965 Fay, et a1. 100/214 Primary Examiner-Lowell A. Larson Att0rneyWaters, Roditi, Schwartz & Nissen ABSTRACT: An apparatus for the axial compression of windings in electrical machines and power transformers, during the manufacture thereof, is provided with a plurality of mechanisms for developing a compressive force. Each mechanism includes at least one arm having a free lower end adapted to slidingly engage a surface. The arms are each inclined at an acute angle relative to the surface. The mechanisms further include a vertically extending rod for transmitting a compressed force to the winding. The rod is connected at its lower end tothe upper ends of the arms such that the weight of the winding acts to decrease the acute angle of the arms with the surface whereby the rod is pulled down to produce a desired axial compressed force.

PATENTEUJANZGIQYI 3,557,846

SHEEI 1 [1F 3 APPARATUS FOR AXIAL COMPRESSION OF WINDINGS The present invention relates to apparatus for the axial compression of the windings of electrical machines, particularly, the windings of power transformers.

In known apparatus axial compression of the windings of power transformers is performed with the help of disc-shaped springs or with the help of hydraulically actuated clamping mechanisms.

However, the known apparatus are not free from certain disadvantages, namely: disc-shaped springs do not provide for high-quality axial compression of the windings because the compressive force sharply decreases at the final stage of compression, whereas the hydraulically actuated mechanisms are of a complicated design, expensive in manufacture and not sufficiently reliable in operation.

It is an object of the present invention to overcome these disadvantages.

The present invention relates to an apparatus for the axial compression of the windings of electrical machines and, particularly, of the windings of large-capacity power transformers, featuring uncomplicated design, reliable operation, and in which the compression is performed by the weight of the windings and the fixtures associated therewith.

This is attained in an apparatus the axial compression of the windings of electrical machines, particularly, those of power transformers, comprising a plurality of clamping mechanisms for generating a compressive force, in which apparatus, according to the present invention, each said clamping mechanism includes at least one arm of which the lower end slidingly engages a supporting structure, said arm being inclined at an acute angle with respect to the supporting surface of said structure, said clamping mechanism further including a vertically extending rod for the axial compression of said windings, the lower end portion of said rod being operatively connected to the upper end portion of said arm in such manner that in the course of compression the weight of the winding being processed is transmitted to said arm, tending to decrease the angle of inclination, whereby said vertically extending rod is pulled down, thus producing the compressive force.

In a preferred embodiment of the present invention the operating connection between the lower end portion of said rod and the upper end portion of said arm is established through a gear-and-rack transmission, the arm being preferably telescopic.

An apparatus constructed in accordance with the teaching of the present invention, develops a comparatively small compression force in the initial stage of compressing a winding, whereas during the final stage it develops a maximum desired force without the use of high-capacity hydraulic presses.

The present invention will be better understood from the following detailed description of a preferred embodiment thereof, due reference being made to the accompanying drawings, in which:

FIG. 1 shows a single clamping mechanism of an apparatus for the axial compression of transformer windings, according to the invention;

FIG. 2 is a top view of the mechanism of the FIG. 1;

FIG. 3 shows the general view of an apparatus for the axial compression of transformer windings, prior to their drying;

and FIG. 4 shows an apparatus, similar to that shown in FIG. 3 adapted for the axial compression of transformer windings in the course of their drying.

The present invention will be described in connection with its applications for the axial compression of transformer windings, as part of the process of manufacturing the same (immediately after their having been wound and in the course of their drying).

As shown in FIGS. 1, 2 and 3, an apparatus for the axial compression of the windings of power transformers has four clamping mechanisms, of which each one comprises a body 1, arms 2 made integral with'toothed'segments 3, support rollers 4 and a vertical rod 5 havinga toothed rack '6 rigidly attached to-its lower end portion. A nut 7 is screwed on the. threaded upper end portion of the rod 5 for securing a winding to be compressed.

In the embodiment herein described each one of the clamping mechanisms has two arms 2, although only one arm is necessary.

The toothed segments 3 of the arms 2 mesh with the teeth of the toothed rack 6, which can move up and down when the arms pivot. The arms 2 bear against the supporting surface 8 by their support rollers 4, the arms being inclined at an acute angle to this surface.

This inclination angle a is chosen in accordance with a desired initial force of compressing a winding, and also with a desired axial extent of the compression (i.e. the vertical travel h of the toothed rack 6).

When a winding is dried inside a drying chamber (FIG. 4), the compressive force depends on the weight of the winding and its fixtures, and also on the ratio of the throws A and B of the arm 2. Moreover, when a winding is to be axially compressed outside a drying chamber, immediately after its having been wound (FIG. 3), the compressive force additionally depends on the force developed by the returning piston of a hydraulic cylinder.

Total force p of axial compression can be established according to a formula:

where nis the number of clamping mechanisms simultaneously used for compressing a winding;

i-is the ratio of the throws A and B of the arms 2;

Qis the total vertical load applied to the anns 2 during compression and including: the weight of the winding and of the clamping mechanisms with all the fixtures (the mandrel, the pressing plates, the tightening pins, etc.) and also, when the winding is compressed outside a drying chamber, the force developed by the hydraulic cylinder.

a-is the angle of inclination of the arms 2 with respect to the supporting surface.

The apparatus embodying the present invention operates, as follows.

A winding 9 (FIG. 3) is brought to the axial compression device from a winding machine,) with the winding assembled with the pressure plates 10 and 11, tightened with pins 12 and nuts I3. The winding is put onto the supporting surface 8, after which a hydraulic cylinder 14 is actuated to raise the winding to a height I-I" sufficient for introducing the clamping mechanisms therebeneath. The clamping mechanisms are placed beneath the pressure plate 10, and their vertical rods 5 are passed through slots 15 provided in the pressure plates 10 and 11 especially for that purpose, whereafter nuts 7 are screwed onto the threaded upper end portion of the rods 5 and tightened against the top pressure plate 1 1. Then the hydraulic cylinder 14 is actuated for its return stroke, whereby its piston rod 16 and the winding-carrying table 17 secured on the lastmentioned rod are lowered into their bottom position, until the support rollers 4 ofthe clamping mechanisms engage from above the supporting surface 8. Now the weightof the winding and the fixtures is applied to the arms 2 of the clamping mechanisms, and the arms 2 start spreading apart and driving down the toothed racks 6 (FIG. 1). With the racks 6 going down, the winding 9 is axially compressed, because the top pressure plate 11 is brought down by the vertical rods 5 rigidly attached to the racks 6 (in this embodiment the rods 5 have their threaded lower end portions screwed into the threaded bores of the sacks 6). As a result of the axial compression the pins 12 will become loose, and their nuts 13 should be retightened accordingly.

If needed, this operation of axial compression can be repeated several times. This can be done easily merely by raising the-winding with the help of the hydraulic cylinder 14 and then letting the winding lower'under its own weight. Incase the weight of the winding and its fixtures proves insufficient for adequate axial compression of the winding, a desired compression force can be achieved by: making use of the force developed by the piston 16 ofthe hydraulic cylinder 14 during the return stroke thereof, and also either by adding some extra weight from above or by adjusting the effective throw 8" of the arm 2 (FIG. 1).

After the axially compressed winding 9 assembled with the clamping mechanisms is removed from the device for axial compression outside the drying chamber (FIG. 3), it can be loaded onto a loading trolley 18 (F IG. 4) which is then driven into a drying chamber 19. This loading trolley 18 can carry several windings of different types, all assembled with their clamping mechanisms. As shown in FIG. 4, the clamping mechanisms require a modest amount of space, since they project by a small distance beyond the bottom pressure plate It).

Axial compression of the winding 9 in the course of its drying goes on, as follows. As the winding is being dried, its axial dimension decreases and it is compressed between the pressure plates 10 and 11, exactly as it has been already described in connection with the axial compression outside the drying chamber. It should be pointed out, that with the inclination angle a of the arms 2 decreasing, the force of axial compression is increased and reaches its desired maximum value when the angle is brought down to zero (the arms 2 lie flat on the supporting surface). Again, the compression force depends on the total weight of the winding and its fixtures and on the ratio of the effective throws A and B of the arms 2 of the clamping mechanisms. When the drying is over, the trolley 18 with the winding 9 on it is rolled out from the drying chamber, the nuts 13 of the pins 12 spaced about the perimeter of the winding 9 are tightened, the clamping mechanisms are removed, and the winding 9 can be forwarded to the next operation (removing the mandrel or assembling with other parts).

Described hereinabove is but one ofmany possible practical embodiments of the invention.

Moreover, the above-described clamping mechanism, a device for the axial compression of windings, may comprise various equivalent modifications of clamping mechanisms of the similar arm-and-lever kind.

Thus, for example, each one of the clamping mechanisms can have one or two arms connected to the vertically extending rods by means of one or two pivot pins received in the corresponding grooves provided in the lower end portions of the rods, or by means of cam-andfollower mechanisms or shackles.

We claim:

1. An apparatus for the axial compression of windings in electrical machines and power transformers, said apparatus comprising a plurality of means for developinga compressive force, each one of said means comprising at least one arm of which the free lower end slidingly engages a supporting surface, said arm being inclined at an acute angle relative to said surface, said means further including avertically extending rod for transmitting vertical compressive force to a winding being compressed, said rod having its lower end portion operatively connected with the upper end portion of said arm such that in the course of compression the weight of said winding acts upon said arm to decrease the acute angle of inclination of said am with said surface, whereby said vertically extending rod is pulled down to produce a desired axial compressive force.

2. An apparatus as claimed in claim 1, wherein said lower end of said vertically extending rod is operatively connected to said upper end of said arm through rack-and-gear means.

3. An apparatus as claimed in claim 1, wherein each one of said arms is telescopically extensible. 

1. An apparatus for the axial compression of windings in electrical machines and power transformers, said apparatus comprising a plurality of means for developing a compressive force, each oNe of said means comprising at least one arm of which the free lower end slidingly engages a supporting surface, said arm being inclined at an acute angle relative to said surface, said means further including a vertically extending rod for transmitting vertical compressive force to a winding being compressed, said rod having its lower end portion operatively connected with the upper end portion of said arm such that in the course of compression the weight of said winding acts upon said arm to decrease the acute angle of inclination of said arm with said surface, whereby said vertically extending rod is pulled down to produce a desired axial compressive force.
 2. An apparatus as claimed in claim 1, wherein said lower end of said vertically extending rod is operatively connected to said upper end of said arm through rack-and-gear means.
 3. An apparatus as claimed in claim 1, wherein each one of said arms is telescopically extensible. 